共查询到20条相似文献,搜索用时 31 毫秒
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本文评述了近年来发展起来的扩展X射线吸收精细结构(EXAFS)谱的理论、实验及数据分析方法,对于EXAFS的应用作了介绍,也对EXAFS的优点、局限性及发展的相关技术进行了讨论。 相似文献
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P. Lagarde 《Il Nuovo Cimento D》1984,3(5):885-902
Summary A review of some general trends of EXAFS in alloys and metallic glasses is given. The intrinsic qualities of the EXAFS method
in metallurgy, structure of amorphous materials, clustering and spin glasses are discussed.
Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981. 相似文献
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A theory program intended for use with extended X‐ray‐absorption fine structure (EXAFS) spectroscopy and based on the popular FEFF8 is presented. It provides an application programming interface designed to make it easy to integrate high‐quality theory into EXAFS analysis software. This new code is then used to examine the impact of self‐consistent scattering potentials on EXAFS data analysis by methodical testing of theoretical fitting standards against a curated suite of measured EXAFS data. For each data set, the results of a fit are compared using a well characterized structural model and theoretical fitting standards computed both with and without self‐consistent potentials. It is demonstrated that the use of self‐consistent potentials has scant impact on the results of the EXAFS analysis. 相似文献
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T. M. Hayes 《Il Nuovo Cimento D》1984,3(5):803-815
Summary Extended X-ray absorption fine-structure (EXAFS) spectroscopy has been demonstrated to be a most useful probe of short-range
interatomic correlations in a wide variety of materials. The theory of the EXAFS is presented in its simplest form so as to
provide the basis for a discussion about the kind and quality of the structural information which can be extracted from EXAFS
data. The adequacy of several of the approximations commonly incorporated in this theory is examined with emphasis on those
areas of the theory which bear most directly on the analysis of EXAFS data.
Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981. 相似文献
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Summary The authors discuss the information on the radial-distribution function (RDF) obtainable from EXAFS as compared with X-ray
diffraction. The cases of Gaussian and non-Gaussian RDFs are illustrated showing how the Fourier transform (FT) of the experimental
spectrum is connected with the RDF parameters in the two cases. The evidence of an asymmetric RDF in a metal glass, Fe80B20, is presented and discussed in detail.
Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981. 相似文献
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Summary We analyse the effect of the statistical noise on the physical parameters derived from an EXAFS spectrum. Two separate classes
of experimental cases are discussed, namely heavy and light backscatterers. The weight of the noise in the two cases is, in
fact, quite different, depending on thek range useful for the analysis of the data. We find that for heavy backscatterers the statistical noise can usually be neglected,
while for light backscatterers it can be one of the main limitations in obtaining reliable results from EXAFS.
Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981. 相似文献
9.
The Landweber iteration approach is used to construct the radial pair distribution function (RPDF) from an X‐ray absorption (EXAFS) spectrum. The physical motivation for the presented investigation is the possibility to also reconstruct asymmetric RPDFs from the EXAFS spectra. From the methodical point of view the shell fit analysis in the case of complicated spectra would be much more eased if the RPDF for the first shell(s) are computed precisely and independently. The RPDF, as a solution of the fundamental EXAFS integral equation, is examined for theoretical examples, and a detailed noise analysis is performed. As a real example the EXAFS spectrum of curium(III) hydrate is evaluated in a stable way without supplementary conditions by the proposed iteration, i.e. by a recursive application of the EXAFS kernel. 相似文献
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In real systems, inelastic processes remove photoelectrons from the elastic scattering channel. This reduces the amplitude of the EXAFS. Traditionally the discrepancies between experimental and theoretical amplitudes were treated by including two semi-empirical reduction factors in the data analysis. Some inelastic effects may, however, be modelled more rigorously using a complex exchange and correlation potential, for example the Hedin-Lundqvist (HL) potential used in most EXAFS data-analysis programs. In this paper a systematic study of the effects of the HL potential on the calculated EXAFS amplitudes is presented. Expressions are derived whereby the EXAFS amplitudes may be examined in the presence of an arbitrary complex potential independently to the rest of the EXAFS signal. These results are used to study the effects of the HL potential on EXAFS data analysis in detail. 相似文献
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R. G. Valeev A. N. Deev E. A. Romanov V. V. Kriventsov A. N. Beltyukov N. A. Mezentsev A. A. Eliseev K. S. Napolskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(4):645-648
A novel approach is presented for synthesis of ZnSe nanodot arrays by physical vapor deposition on porous aluminum oxide templates
with ordered channels. The structure of nanodots was studied by scanning electron microscopy and EXAFS spectroscopy. Data
were obtained for the sizes of nanodots in the array and local atomic structure parameters, i.e., the interatomic distances
and coordination numbers, in comparison with the data for the ZnSe film synthesized on a smooth surface of nonporous Al2O3. 相似文献
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S. Decoster C. J. Glover B. Johannessen R. Giulian D. J. Sprouster P. Kluth L. L. Araujo Z. S. Hussain C. Schnohr H. Salama F. Kremer K. Temst A. Vantomme M. C. Ridgway 《Journal of synchrotron radiation》2013,20(3):426-432
Lift‐off protocols for thin films for improved extended X‐ray absorption fine structure (EXAFS) measurements are presented. Using wet chemical etching of the substrate or the interlayer between the thin film and the substrate, stand‐alone high‐quality micrometer‐thin films are obtained. Protocols for the single‐crystalline semiconductors GeSi, InGaAs, InGaP, InP and GaAs, the amorphous semiconductors GaAs, GeSi and InP and the dielectric materials SiO2 and Si3N4 are presented. The removal of the substrate and the ability to stack the thin films yield benefits for EXAFS experiments in transmission as well as in fluorescence mode. Several cases are presented where this improved sample preparation procedure results in higher‐quality EXAFS data compared with conventional sample preparation methods. This lift‐off procedure can also be advantageous for other experimental techniques (e.g. small‐angle X‐ray scattering) that benefit from removing undesired contributions from the substrate. 相似文献
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T. M. Hayes 《Il Nuovo Cimento D》1984,3(5):816-824
Summary The procedures required in the analysis of extended X-ray absorption fine-structure (EXAFS) data inr space are examined in some detail with reference to comparable operations ink space where appropriate. Since each operation in one space has its exact equivalent in the other, the choice betweenr andk space turns on relative convenience in the particular circumstances of each application. Some potential difficulties are
identified.
Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981. 相似文献
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The aim of the present work is to make a comparative study of the EXAFS spectra recorded at the BL-8 dispersive EXAFS beamline at 2 GeV Indus-2 synchrotron source at RRCAT, Indore (India) with those recorded at other synchrotron EXAFS beamlines, viz., X-19A at NSLS, BNL (USA), EXAFS wiggler beamline 4-1 at the SSRL (USA) and beamline 11.1 at ELETTRA (Italy). For this purpose, EXAFS spectra at Cu K-edge in copper metal have been recorded at these four beamlines. Further, EXAFS spectra at Cu K-edge in a copper complex have also been recorded at BL-8 beamline and beamline 11.1 at ELETTRA (Italy). The obtained experimental μ(E) data have been background-subtracted and then normalized. The normalized data have been then converted to χ(k) data, which have been Fourier-transformed and then fitted with the theoretical model, thereby yielding different structural parameters. It has been shown that the results obtained from the EXAFS spectra recorded at the BL-8 beamline are comparable with those obtained from other synchrotron EXAFS beamlines and also with the crystallographic results reported by earlier workers. The reliability, usefulness and data quality of the BL-8 beamline have been discussed. 相似文献
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本文对EXAFS方法在金属玻璃结构研究中所得径向距离的误差进行了分析。所做的模拟计算表明当前流行的关于这个问题的误差理论不能圆满地解释这一现象。本文分析了玻璃态和晶态的相移函数,指出在相似的体系中玻璃态和晶态相移函数与k的关系采用线性函数近似时,其斜率可能是不同的,而且无序度相差越大,两者的偏差可能也越大。在EXAFS数据处理过程中,没有考虑这种偏差的影响是造成EXAFS方法结果中径向距离误差的一个原因。本文还提出了一个修正参考样品(晶态)相移函数斜率偏差的方法,并将它应用于Cu55Zr45金属玻璃的EXAFS数据处理中,所得结果与用X射线异常散射方法测定的结果符合得很好。
关键词: 相似文献
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T. S. Bush A. V. Chadwick C. R. A. Catlow G. N. Greaves R. A. Jackson 《辐射效应与固体损伤》2013,168(2):487-492
Abstract Preliminary results of a combined EXAFS and computer simulation study of rare-earth doped β″-alumina are presented. 相似文献
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Simple, but general, model calculations are presented to show that two or more similar (but slightly different) bondlength contributions of different amplitude can lead to substantial errors in an EXAFS measurement with the apparent bondlength falling outside the ranges of the actual bondlengths. The effect is most acute for short data ranges, common in Surface EXAFS, and for low symmetry adsorption sites of the type likely to occur in many molecular adsorption systems. 相似文献
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G. Dalba N. Daldosso D. Diop P. Fornasini R. Grisenti F. Rocca 《Journal of luminescence》1998,80(1-4):103-107
The local structure of porous silicon has been studied exciting its optical luminescence by X-rays (XEOL). The photoluminescence yield and the total electron yield (TEY), recorded simultaneously as a function of the X-ray energy at the Si K edge, give rise to the extended X-ray absorption fine structures (EXAFS). Analysis of EXAFS data confirms that the optical luminescence of porous Si originates from the nanocrystalline cores and shows that XEOL–EXAFS and TEY–EXAFS are sensitive to different Si local environment. It can be assumed that XEOL–EXAFS is related only to the light emitting sites while TEY–EXAFS is sampling both luminescent and non-luminescent Si sites. 相似文献